Hirayama’s Disease- A Case Study

Abstract

Hirayama disease, a condition with male preponderance also known as monomelic amyotrophy was first described by Hirayama in 1959. Highest prevalence of this condition is noted in Asian population with most cases reported from Japan. Cases have also been reported from other parts of Asia and few from European countries. It is a form of motor neuron disease that has an insidious onset and presents as unilateral or bilateral muscle atrophy and weakness without sensory loss.¹ This condition usually progresses for one to two years before plateauing. There are chronic ischaemic changes taking place in the anterior horn cells of the cervical region, especially in the C7 and C8 regions leading to myelopathy.¹ Imbalance between the vertebral column and dural canal during growth spurt is postulated to be the cause.^1,5  This imbalance causes increased laxity causing anterior displacement of posterior dura during flexion causing mechanical cord compression.^1,5 Even though the disease is non-progressive, management of symptomatic myelopathy is required. The use of a cervical collar and prevention of neck flexion is the first line of treatment.¹ If conservative methods fail, surgical intervention may be considered.¹ A study by YeTian reported that there was an association between posterior cervical extensors and cervical kyphosis. They concluded that weakness of posterior cervical extensors (deep and superficial) leads to poor cervical stability which was crucial in the management of HD.⁸ The focus of this study is cervical muscle strengthening and core strengthening to improve spinal alignment.